Parenteral delivery of various drugs has become a desired method of drug delivery for a number of reasons. Drug delivery by injection may enhance the effect of the substance being delivered and ensure that the unaltered medicine reaches its intended site at a significant concentration. Additionally, undesired side effects associated with other routes of delivery, such as systemic toxicity, may be minimized through parenteral delivery. Bypassing the digestive system of a mammalian subject avoids digestive degradation, absorption difficulties and first-pass metabolism issues, thereby enhancing delivery of a necessary amount of drug, at a desired concentration, to the targeted site.
Traditionally, manually operated syringes and injection pens have been employed for delivering parenteral drugs to a patient. More recently, the parenteral delivery of liquid medicines has been accomplished by several means, including bolus injections that use a needle and a reservoir, gravity driven dispensers, or transdermal patch technologies. Bolus injections often imperfectly match the clinical needs of the patient, however, and usually require larger individual doses than are desired at the specific time of administration. Continuous delivery of medicine through gravity-feed systems may compromise a patient's mobility and lifestyle, and may limit the therapy to simplistic flow rates and profiles. Transdermal patches also have restrictions in requiring specific molecular drug structures for efficacy, and the control of the drug administration through a transdermal patch is often severely limited.
Compared to these approaches to parenteral administration, pump type delivery devices (e.g., ambulatory infusion pumps), can be significantly more convenient for patients, because drug doses may be calculated and delivered automatically to a patient at any time during the day or night. Further, when used in conjunction with metabolic sensors or monitors, pumps can be controlled automatically to provide need-based doses of a fluidic medium based on sensed or monitored metabolic levels. These infusion devices may thus offer sophisticated fluid delivery profiles, accomplishing bolus requirements, continuous infusion and variable flow rate delivery. The infusion capabilities usually result in better efficacy of the drug and therapy and less toxicity. As a result, infusion devices have become an important aspect of modern medical treatments of various types of medical conditions, such as diabetes.
Unfortunately, many current ambulatory infusion devices are expensive, difficult to program and prepare for infusion; and tend to be bulky, heavy and fragile. Additionally, filling these devices can often be difficult, and require the patient to carry both the intended medication as well as filling accessories. These devices often require specialized care, maintenance, and cleaning to assure proper function and safety for their intended long-term use, and are not cost-effective for patients or healthcare providers. Hence, although pump type delivery systems have been used to solve a number of patient needs, manually operated syringes and injection pens still remain a preferred choice for drug delivery because they provide integrated safety features, and can more easily identify the status of drug delivery such as the end of dose dispensing. Manually operated syringes and injections pens are not universally applicable, however, and are not preferred for delivery of all drugs. Therefore, there remains a need for an adjustable, or programmable, infusion system that is precise and reliable and can offer clinicians and patients a small, low cost, light weight, simple to use alternative for parenteral delivery of liquid medicines.